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[Delisting Report]

Section 3 - Conclusions

3.1 - Conclusions and Recommendations

B‑26 consists of a trench area with a soil mound at each end. The dates of its usage are unknown and it is presently inactive. It was suspected of being a previous waste disposal site due to a visually apparent trench and the presence of a small geophysical anomaly within the trench.

In March 2000, surface soil and subsurface Glen Rose Limestone samples were collected at five locations. None of the soil samples contained contaminants of concern at concentrations above RRS1 criteria.

For Glen Rose Limestone samples, zinc and chromium were the only metals for which the sample analytical results were greater than the CSSA background level. Two chromium concentrations of 9.7 mg/kg and 8.6 mg/kg, exceeded the background concentration of 8.1 mg/kg. Zinc concentrations of 11.9 mg/kg, 13.9 mg/kg, 14.8 mg/kg, and 17.5 mg/kg for Glen Rose Limestone also slightly exceeded the RRS1 background concentration of 11.3 mg/kg.

A single SVOC, DEHP, which is a common laboratory contaminant, was detected above RRS1 in Glen Rose Limestone. All reported VOC concentrations were below RRS1.

Although chromium and zinc concentrations slightly exceed background in several subsurface (Glen Rose Limestone) samples, the concentrations were below the Texas-specific median background concentrations and are not likely to be the result of past waste management activities. Therefore, further work to address these metals levels is not recommended. In addition, further work to address the detections of the common laboratory contaminant, bis(2-ethylhexyl)phthalate is not recommended. Since B‑26 and the surrounding area did not indicate any evidence of waste management activity, the subsurface analytical results should be included in the data set for CSSA background calculations.

A single small piece of tin, discovered in the subsurface at the location of the northwestern geophysical anomaly, was removed. The tin appears to be a random piece of scrap metal and not associated with waste management activities. Therefore, due to SWMU B‑26 having no confirmed evidence of waste management activities at the site, it should be delisted and removed from further considerations.